Emulsified perfluorochemicals are effective carriers of oxygen in biological systems. Many factors, however, affect the degree to which they are effective. A number of different combination of emulsified perfluorochemicals, oncotic agents, electrolytes, and nutrients will be used for the total exchange perfusion of animals. The "bloodless" animals will be further slowly perfused to keep all normal blood protein and cellular constituents at low concentrations. The perfusions will be continued for as long as possible, making modifications in the preparations as needed to maintain suitable pH, pCO2, values, blood volume, and concentrations of important non-protein constituents. The kinds and amounts of proteins and numbers of cellular elements lost during the prolonged perfusions will be determined. Repeated exchange perfusions of a given animal will be carried out at daily or multiple day intervals, and the influence of this treatment on blood component production by the animals will be studied. Other animals will be totally perfused and then allowed to regenerate their blood cells and proteins. The kinetics of the regeneration will be studied and means of altering the regeneration rates will be sought. The metabolic and morphological integrity of the tissues of exchange perfused animals will be determined at selected post-perfusion intervals. The long-term perfusion of organs in vitro will be investigated using different kinds of perfluorochemical-containing mixtures.